3,887 research outputs found
The Unreasonable Success of Local Search: Geometric Optimization
What is the effectiveness of local search algorithms for geometric problems
in the plane? We prove that local search with neighborhoods of magnitude
is an approximation scheme for the following problems in the
Euclidian plane: TSP with random inputs, Steiner tree with random inputs,
facility location (with worst case inputs), and bicriteria -median (also
with worst case inputs). The randomness assumption is necessary for TSP
On the Chacteristic Numbers of Voting Games
This paper deals with the non-emptiness of the stability set for any proper voting game.We present an upper bound on the number of alternatives which guarantees the non emptiness of this solution concept. We show that this bound is greater than or equal to the one given by Le Breton and Salles [6] for quota games.voting game, core, stability set
Speed of coming down from infinity for birth and death processes
We finely describe the speed of "coming down from infinity" for birth and
death processes which eventually become extinct. Under general assumptions on
the birth and death rates, we firstly determine the behavior of the successive
hitting times of large integers. We put in light two different regimes
depending on whether the mean time for the process to go from to is
negligible or not compared to the mean time to reach from infinity. In the
first regime, the coming down from infinity is very fast and the convergence is
weak. In the second regime, the coming down from infinity is gradual and a law
of large numbers and a central limit theorem for the hitting times sequence
hold. By an inversion procedure, we deduce that the process is a.s. equivalent
to a non-increasing function when the time goes to zero. Our results are
illustrated by several examples including applications to population dynamics
and population genetics. The particular case where the death rate varies
regularly is studied in details.Comment: 30 pages. arXiv admin note: text overlap with arXiv:1310.740
The Physics of Glueballs
Glueballs are particles whose valence degrees of freedom are gluons and
therefore in their description the gauge field plays a dominant role. We review
recent results in the physics of glueballs with the aim set on phenomenology
and discuss the possibility of finding them in conventional hadronic
experiments and in the Quark Gluon Plasma. In order to describe their
properties we resort to a variety of theoretical treatments which include,
lattice QCD, constituent models, AdS/QCD methods, and QCD sum rules. The review
is supposed to be an informed guide to the literature. Therefore, we do not
discuss in detail technical developments but refer the reader to the
appropriate references.Comment: Invited review for Int. J. Mod. Phys. E, 32 pages, 12 figures, 8
table
Analysis of Quasi-Cyclic LDPC codes under ML decoding over the erasure channel
In this paper, we show that Quasi-Cyclic LDPC codes can efficiently
accommodate the hybrid iterative/ML decoding over the binary erasure channel.
We demonstrate that the quasi-cyclic structure of the parity-check matrix can
be advantageously used in order to significantly reduce the complexity of the
ML decoding. This is achieved by a simple row/column permutation that
transforms a QC matrix into a pseudo-band form. Based on this approach, we
propose a class of QC-LDPC codes with almost ideal error correction performance
under the ML decoding, while the required number of row/symbol operations
scales as , where is the number of source symbols.Comment: 6 pages, ISITA1
Hybrid meson masses and the correlated Gaussian basis
We revisited a model for charmonium hybrid meson with a magnetic gluon [Yu.
S. Kalashnikova and A. V. Nefediev, Phys. Rev. D {\bf 77}, 054025 (2008)] and
improved the numerical calculations. These improvements support the hybrid
meson interpretation of X(4260). Within the same model, we computed the hybrid
meson mass with an electric gluon which is resolved to be lighter. Relativistic
effects and coupling channels decreased also the mass.Comment: 9 pages, 20 figures ; accepted for publication in Phys. Rev.
On the performance of the Shapley Shubik and Banzhaf power indices for the allocations of mandates
A classical problem in the power index literature is to design a voting mechanism such as the distribution of power of the different players is equal (or closer) to a pre established target. This tradition is especially popular when considering two tiers voting mechanisms: each player votes in his own jurisdiction to designate a delegate for the upper tier; and the question is to assign a certain number of mandates for each delegate according the population of the jurisdiction he or she represents. Unfortunately, there exist several measures of power, which in turn imply different distributions of the mandates for the same pre established target. The purposes of this paper are twofold: first, we calculate the probability that the two most important power indices, the Banzhaf index and the Shapley-Shubik index, lead to the same voting rule when the target is the same. Secondly, we determine which index on average comes closer to the pre established target.Banzhaf, Shapley-Shubik, power indices
- âŠ